Curable composition based on branched acrylates with carboxyl groups and/or branched acrylates with epoxide groups and aminoplast resins

ABSTRACT

Curable composition based on branched acrylates with COOH groups and/or branched acrylates with epoxide groups, and aminoplast resins. 
     The present invention relates to a curable composition consisting of 
     A) a polymer with at least 2 COOH groups, 
     B) a polymer with at least 2 epoxide groups and 
     C) an aminoplast resin. 
     At least one of components A) or B) is based on a branched soluble acrylate copolymer, more than 3 to 30% by weight, based on the total weight of the monomers, of a monomer with at least two polymerizable, olefinically unsaturated double bonds being used in the preparation of these branched acrylate copolymers and the proportions of the individual components relative to one another being chosen so that a molar ratio of 3:1 to 1:3 prevails between the carboxyl groups of component A) and the epoxide groups of component B) and a weight ratio of 65:35% by weight to 98:2% by weight prevails between the epoxy resin component and the aminoplast resin component. 
     The invention also relates to coating agents based on the curable composition.

The invention relates to a curable composition based on branched solubleacrylate copolymers which are obtainable by copolymerization of monomershaving at least two polymerizable olefinic unsaturated double bonds,functional groups-carrying monomers, and additional polymerizablemonomers with an olefinic unsaturated double bond.

From the class-forming EP-A 103 199 an acrylate copolymer is known whichis obtained by copolymerization of 10 to 95 percent by weight oftert-butyl acrylate, 0.1 to 3 percent by weight of polyfunctionalmonomers such as, for example, trimethylolpropane-triacrylate, 1 to 30percent by weight of monomers having a functional group, and 0 to 80percent by weight of additional polymerizable ethylenic unsaturatedmonomers. As comonomers with a functional group are named inter aliacarboxyl groups-containing monomers such as acrylic acid and methacrylicacid. From this publication, furthermore, a coating composition is knownwhich contains a carboxyl groups-containing acrylate copolymer branchedby polymerizing into it multiply ethylenic unsaturated monomers and apolyepoxide as cross-linking agent. The described branched acrylatecopolymers lead to coatings with good resistance to weather, inparticular good resistance to moisture which can be traced back to thecontent of monopolymerized tert-butyl acrylate.

From DE-P 30 22 996 is known an annealing lacquer in the case of whichcarboxyl groups-containing polymers, such as for example acrylates basedon acrylic acid or methacrylic acid and glycidyl groups-containingacrylates can be mixed to form a curable composition. This leads tofilms with greater hardness and resistance to weather.

In WO 84/00771 a multi-component system is described in which a total offour types of binding agents or components are mixed with each other andthen applied; the components are:

a) OH-acrylate,

b) acid anhydride, wherein at least 50 percent arealkylhexahydrophthalic anhydride,

c) epoxide resin, and

d) melamine resin.

No statements are made regarding the potlife of the mixture; particularadvantage compared to conventional systems is said to be the high solidon application, partially greater than 70 percent solid matter.

In DE-OS 23 33 384 a binding agent based on acrylated polyesters isdescribed, i.e. in an OH polyester (or alkyd resin) an OH acrylate ispolymerized with relatively low acid number, wherein the cross linkingcan be carried out with melamine resins and simultaneously epoxideresins can be carried out. The proportions are: 60 to 70% OH copolymer,20 to 30% melamine resin, 5 to 15% epoxide resin.

Advantages compared to existing systems are said to be: improvedresistance to weather (therefore low-aroma acrylate), improvedresistance to solvents and improved tendency of the lacquers to run onvertical surfaces.

The task of the present invention consisted in combining all positiveproperties of the known coating materials in a curable composition, inparticular to achieve the porperties of the coating materials from theaspect of their resistance to long-term stress by solvents, chemicals,water or water vapor as well as to achieve simultaneously good hardnessand elasticity. Furthermore, for reasons of economy a high solid contentof the curable coating material is to be achievable at relatively lowviscosity.

This task is solved, surprisingly, by a curable composition whichconsists of carboxyl groups-containing polymers, epoxidegroups-containing polymersand aminoplastic resins, and wherein theepoxide component and/or the carboxyl component is based on a solublebranched acrylate copolymer whichhas a higher fraction ofmonopolymerized multiply ethylenic unsaturated monomers than theacrylate resin described in EP-A-103 199. In contrast tolinear acrylateresins and the acrylate resins from EP-A-103 199 in the case of theacrylate copolymers according to the invention a lower viscosity atrelatively high solid content can be achieved. Through the highlybranched structure of the copolymer the functional groups of theacrylate resin become more reactive which carries with it a greatadvantage.

Subject matter of the present invention is a curable compositioncomprising:

A) a polymer having at least two --COOH groups,

B) a polymer having at least two epoxide groups, and

C) an aminoplastic resin characterized in that at least one of thecomponents A) or B) is based on a branched soluble acrylate copolymer,

wherein the production of this branched acrylate copolymer 5 to 30percent by weight, relative to the total weight of the monomers, of amonomer withat least two polymerizable olefinic unsaturated double bondsare used and wherein the proportions of the individual components toeach other are so selected that between the carboxyl groups of thecomponent A) and the epoxide groups of the component B) a molar ratio of3:1 to 1:3 obtains andbetween the epoxide resin component and theaminoplastic resin component a ratio of weight of 65:35 percent byweight to 98:2 percent by weight.

According to an embodiment of the invention the component A) is based ona soluble branched copolymer obtainable by copolymerization of

al) 5 to 30 percent by weight, preferred are 5 to 25 percent by byweight, of a monomer with at least two polymerizable olefinicunsaturated double bonds,

a2) 3 to 50 percent by weight, preferred are 8 to 40 percent by weight,of a carboxyl groups-containing monomer,

a3) at least 40 percent by weight of additional monomers with apolymerizable olefinic unsatured double bond,

wherein the sum of a1), a2), and a3) is 100 percent by weight, in anorganic solvent at 70° to 1300° C., preferably at 80°to 120° C., withthe use of at least 0.5 percent by weight, preferably at least 2.5percent by weight, relative to the total weight ofthe monomers, of apolymerization regulator and with the use of polymerization initiators,wherein the polymerization for the production of the acrylate copolymeris carried out so that a solution of the polymerwith a solid content of40 to 65 percent by weight results.

As component a1) can be used advantageously compounds of the generalformula ##STR1##in which R=H or CH₃

X=O, NR', S with R'=H, alkyl, aryl

n=2 to 8.

Examples of such compounds are hexanediol diacrylate, hexanedioldimethacrylate, glycol diacrylate, glycoldidimethacrylate,butanedioldiacrylate, butanedioldimethacrylate,hexamethylenebismethacrylamide, trimethylol propane triacrylate,trimethylol propane trimethacrylate. Suitable are also divinyl compoundssuch as divinyl benzene. It is also possible to use multiply unsaturatedmonomers with a functional group, for example bisacrylamido acetic acid.It is understood that also combinations of the multiply unsaturatedmonomers can be used.

Further possible components a1) are conversion products of a carboxylicacid having a polymerizable olefinic unsaturated double bond andglycidyl acrylate and/or glycidyl methacrylate. It is also possible touse as component a1) a polycarboxylic acid esterified with anunsaturated alcoholcontaining a polymerizable double bond or unsaturatedmonocarboxylic acid. As monomers with at least two polymerizableolefinic unsaturated double bonds conversion products of apolyisocyanate with alcohols or amines containing unsaturatedpolymerizable double bonds are also used. By example the conversionproduct of one mole of hexamethylene diisocyanate with two moles ofallyl alcohol may be cited.

As component a2) β-carboxyethyl acrylate is especially suitable;furthermore, acrylic acid, methacrylic acid, itaconic acid, crotonicacid,aconitic acid, maleic and fumaric acid or their semi-esters arepossible.

The choice of component a3) depends largely on the desired properties ofthe acrylate copolymer with respect to elasticity, hardness,compatibility, and polarity. These properties can be partiallycontrolled with the help of known glass transition temperatures of themonomers. The monomers can be selected from the group comprisingstyrene, vinyl toluene,alkyl ester of acrylic acid and methacrylic acid,alkoxyethyl acrylate as well as esters of maleic, fumaric, crotonic, anddimethyl acrylic acid.

In addition, as component a3) can be used also hydroxylgroups-containing monomers for example hydroxyalkyl esters of acrylicand/or methacrylic acid. It is possible, to use as additional monomerswith a polymerizable olefinic unsaturated double bond 0.1 to 5 percentby weight, relative to the total weight of all monomers, monomers withphosphoric acid groups, also, for example, phosphoric acid esters withpolymerizable double bonds.

It is particularly advantageous if into the acrylate copolymer having anacid number of 20 to 250, preferably 50 to 180, monomers areincorporated containing groups which catalyse a subsequent cross-linkingof the carboxyl groups-containing acrylate copolymer with epoxidegroups, thus, for example, tertiary amino groups.

The present invention relates also to a curable compound characterizedin that as component A) a soluble branched acrylate copolymer is usedwhich is obtainable by copolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds wherein di- and polyesters of di- and polyols with acrylic acidare excluded,

a2) 3 to 50 percent by weight, preferably 8 to 40 percent by weight of acarboxyl groups-containing monomer,

a4) 0.1 to 20 percent by weight, preferred are 1 to 10 percent byweight, of a tertiary amine with a polymerizable olefinic unsaturateddouble bond,

a5) 0 to 40 percent by weight, preferred are 5 to 25 percent by weight,of a hydroxyl groups-containing monomer, and

a3) 0 to 80 percent by weight of further monomers with a polymerizableolefinic unsaturated double bond, wherein the sum of components a1),a2), a3), a4), and a5) is 100 percent by weight, in an organic solventat 70° to 1300° C., preferably at 80° to 120° C.,with the use of atleast 0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and with the use of polymerization initiators, wherein thepolymerization for the production of the acrylate copolymer iscarriedout so that a solution of the polymer with a solid content of 40 to65percent by weight results, wherein the proportions of the individualcomponents to each other are so selected that between the carboxylgroups of the component A) and the epoxide groups of component B) amolar ratio of 3:1 to 1:3 obtains and that between the epoxide resincomponent and theaminoplastic resin component a weight ratio of 65:35percent by weight to 98:2 percent by weight obtains.

As component a1) can be used advantageously compounds of the generalformula ##STR2##in which X=O, NR', S with R'=H, alkyl, aryl

n=2 to 8.

Component a1) can be a conversion product of a carboxylic acid having apolymerizable olefinic unsaturated double bond, wherein acrylic acid isexcluded, and glycidyl methacrylate. Furthermore, monocarboxylic acidswith an unsaturated a polymerizable double bond with the exception ofderivatives of acrylic acid are possible. Advantageously components a1)are selected from products produced from polyisocyanates withunsaturated polymerizable double bonds-containing alcohols or amines.

Examples of ethylenic unsaturated compounds with a tertiary aminogroups, thus for component a4) are N,N'-dimethylaminoethyl methacrylate,N,N'-diethylaminoethyl methacrylate, 2-vinyl pyridine, and 4 vinylpyridine, vinyl pyrroline, vinyl quinoline, vinyl isoquinoline,N,N'-dimethylaminoethyl vinyl ether and 2-methyl-4-vinyl pyridine.

If necessary, hydroxyl groups-containing monomers can be used. Asexamples hydroxyl alkyl esters of acrylic and methacrylic acid may benamed, such as, for example, hydroxyethyl acrylate, hydroxypropylacrylate, hydroxybutyl acrylate, hydroxyamyl acrylate, hydroxyhexylacrylate, hydroxyoctyl acrylate, and the corresponding methacrylatles.The choice ofadditional monomers with a polymerizable olefinicunsaturated double bond takes place from the group already cited above.In this case it is potentially advantageous that as additional monomerswith a polymerizable double bond 0.1 to 5 percent by weight, relative tothe total weight of all monomers, monomers with phosphoric acid groupsare used.

It is particularly preferred if as component A) a soluble branchedacrylatecopolymer is used which is obtainable by copolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds wherein di- and polyesters of di- and polyols with acrylic acidare excluded,

a4) 0.1 to 20 percent by weight, preferred are 1 to 10 percent byweight, of a tertiary amine with a polymerizable olefinic unsaturateddouble bond,

a5) 0 to 40 percent by weight, preferred are 10 to 30 percent by weight,ofhydroxyl groups-containing monomers,

a3) 0 to 80 percent by weight of additional plymerizable monomers withan olefinic unsaturated double bond,

wherein the sum of all monomers is 100 percent by weight, in an organicsolvent at 70° to 1300° C., preferably at 80° to 1200° C., with the useof at least 0.5 percent by weight, preferably at least 2.5 percent byweight, relative to the total weight ofthe monomers, of a polymerizationregulator and with the use of polymerization initiators, wherein thepolymerization for the production of the acrylate copolymer is socarried out that a solution of the polymerresults with a solid contentof 40 to 65 percent by weight, and of

a6) cyclic carboxylic anhydrides,

wherein the proportions of the individual components to each other areso selected that between the carboxyl groups of component A) and theepoxide groups of component B) a molar ratio of 3:1 to 1:3 obtains andthat between the epoxide resin component and the aminoplastic resincomponent aweight ratio of 65:35 percent by weight to 98:2 percent byweight obtains.

As component a1) can be used advantageously compounds of the generalformula ##STR3##in which X=O, NR', S with R'=H, alkyl, aryl

n=2 to 8.

Examples of multiply ethylenic unsaturated compounds arehexanedioldimethacrylate, glycol dimethacrylate, butanedioldimethacrylate, trimethylolpropane trimethacrylate, and divinyl benzene.Advantageously the already cited ethylenic unsaturated compounds canalso be used, provided that they are not di-and polyesters of di- andpolyols with acrylic acid.

As polymerizable tertiary amines those already cited above are possible.

As component a5) are suitable hydroxyl alkyl esters of acrylic and/ormethacrylic acid with a primary hydroxyl group, for example hydroxyethylacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyamylacrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, and thecorresponding methacrylates as well as hydroxyalkyl esters with asecondary --OH group, such as 2-hydroxypropyl acrylate, 2-hydroxy butylacrylate, 3-hydroxybutyl acrylate, and the corresponding methacrylates.

In addition, as component a5) conversion products of acrylic acid and/ormethacrylic acid with the glycidyl esters of a carboxylic acid with atertiary α-carbon atom are possible.

The choice of component a3) is not particularly critical and depends onthedesired properties of the acrylate copolymer. It may be mentionedthat as component a3) also carboxyl groups-containing monomers can beused.

Examples of the component a6) are phthalic anhydride, tetrahydrophthalicanhydride, hexahydrophthalic anhydride, succinic anhydride as well astheir halogenated derivatives.

The invention relates also to a curable composition characterized inthat as component A) a soluble branched acrylate copolymer is used whichis obtainable by copolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weightof amonomer with at least two polymerizable olefinic unsaturated doublebonds,

a7) 1 to 30 percent by weight, preferred are 3 to 20 percent by weight,of monomers with cyclic carboxylic anhydride groups,

a3) 45 to 80 percent by weight of further polymerizable monomers with anolefinic unsaturated dobule bond,

wherein the sum of all monomers is 100 percent by weight, in an organicsolvent at 70° to 1300°C., preferably at 80° to 120° C., by using atleast 0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers,a polymerization regulatorand by using polymerization initiators, wherein the polymerization forthe production of the acrylate copolymer is carriedout so that asolution of the polymer with a solid content of 40 to 65 percent byweight results, and from

a8) compounds which have at least one hydrogen able to react with acidanhydride groups as well as also at least one tertiary amino group,

wherein a part of the carboxylic anhydride can also be converted with amonofunctional compound with active hydrogen and the proportions of theindividual component to each other are so selected that between thecarboxyl groups of component A) and the epoxide groups of component B) amolar ratio of 3:1 to 1:3 obtains and that between the peroxide resincomponent and the aminoplastic resin component a weight ratio of 65:35percent by weight to 98:2 percent by 'weight obtains.

As component a1) are suitable the already cited multiply ethylenicunsaturated monomers including the di- and polyesters of di- and polyolswith acrylic acid.

Examples of monomers with cyclic carboxylic anhydride groups are maleicanhydride or itaconic anhydride.

Choice of component a3) depends on the desired properties of theacrylate copolymer. It may be mentioned that in the present casemonomers with carboxyl groups, thus, for example, acrylic acid ormethacrylic acid are also suitable.

Advantageously, as component a8) alcohols having a tertiary amino groupas well as primary or secondary amines having a tertiary amino group areused. The reactive hydrogen of component a8) can stem from a hydroxylgroup, a primary or secondary amino group or a thiol group.

Examples of alcohols with tertiary amino groups are addition products ofsecondary amines and epoxide compounds. Examples of secondary amines aredimethylamine, diethylamine, dipropylamine, dibutylamine, morpholine andpyrrolidine.

Examples of suitable epoxide compounds are ethylene oxide, propyleneoxide,butylene oxide, styrene oxide, and cyclohexene oxide.

Suitable alcohols with tertiary amino groups obtained in the reaction ofsecondary amines with epoxide compounds, are dimethylaminoethanol,diethylaminoethanol, di-n-propylaminoethanol, diisopropylaminoethanol,di-n-butyl-aminoethanol, N-(2-hydroxyethyl)morpholine,N-(2-hydroxyethyl)piperidine, N-(2-hydroxyethyl)pyrrolidone,N-(2-hydroxyethyl)azeridine, N,N'-dimethyl-2-hydroxypropylamine,N,N'-diethyl-2-hydroxypropylamine, triethanolamine, andtripropanolamine.

Examples of the primary or secondary amines, which contain a tertiaryaminogroup, are N,N'-dialkyl-1,3-propylenediamine, such as for exampleN,N'-dimethyl-1,3-propylenediamine, N,N-diethyl-1,3-propylenediamine,and N,N'-dialkyl-1,4-tetraethylenediamine such as, for example,N,N'-dimethyl-1,4-tetramethylenediamine, andN,N'-diethyl-1,4-tetramethylenediamine. Furthermore,N,N'-dialkyl-1,6-hexamethylenediamine, and N-alkylpiperazine as well as2-aminopyridine, 4-aminopyridine, and N-alkylaminopyridine are possible.

It may be mentioned that a part of the carboxylic anhydride groups canalsobe converted with a monofunctional compound with active hydrogensuch as, for example, alcohols.

According to a preferred embodiment of the invention the component A) isadvantageously obtained by copolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds,

a9) 1 to 30 percent by weight of glycidyl esters of ethylenicunsaturated carboxylic acids and/or glycidyl ethers of olefinicunsaturated compounds,

a3) at least 40 percent by weight of further polymerizable monomers withanolefinic unsaturated double bond,

wherein the sum of all monomers is 100 percent by weight, in an organicsolvent at 70° to 130° C., preferably at 80 to 120° C., by using atleast 0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and by using polymerization initiators, wherein thepolymerization for the production of the acrylate copolymer is socarried out that a solution of the polymer with a solid content of 40 to65 percent by weight results, and from

a10) amines with a secondary amino group or di- or polyamines with atleastone tertiary amino group and a primary or secondary amino groupand/or

a11) carboxylic acids having a tertiary nitrogen atom, and from

a6) cyclic carboxylic anhydrides,

wherein the proportions of the individual components to each other areso selected that between the carboxyl groups of component A) and theepoxide groups of component B) a molar ratio of 3:1 to 1:3 obtains andthat between the epoxide resin component and the aminoplastic resincomponent aratio of weight of 65:35 to 98:2 percent by weight obtains.

As component a1) the already mentioned multiply ethylenic unsaturatedmonomers are possible.

Examples of components a9) are glycidyl esters of acrylic acid ormethacrylic acid as well as allyl and vinyl glycidyl ethers, glycidylvinyl esters or glycidyl allyl esters such as glycidyl vinyl phthalate,glycidyl allyl phthalate.

The choice of component a3) depends on the desired properties of theacrylate copolymer and can be made from the group already cited above.However, no carboxyl groups-containing amino groups-containing monomersshould be used as component a3), since they react with the oxirane groupof component a9). The fraction of hydroxyl groups-containing monomersshould be minimal. If hydroxyl groups are necessary for achieving aparticular polarity of the copolymer, monomers with secondary --OHgroups should be preferred.

Examples of component a10) are imidazole, aminopyridine,N-alkylaminopyridine, Ethylpiperazine, dibutylamine.

Examples of component all) are 3- and 4-dimethylaminobenzoic acid,picolinic acid, and dimethylaminosalicylic acid.

As examples for component a6) phthalic anhydride, tetrahydrophthalicanhydride, hexahydrophthalic anhydride, succinic anhydride as well astheir halogenated derivatives may be named.

According to a preferred embodiment of the invention, component A) canbe asoluble branched acrylate copolymer obtainable by thecopolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds,

a2) 3 to 50 percent by weight, preferred are 8 to 40 percent by weightof acarboxyl groups-containing monomer,

a5) 0 to 40 percent by weight, preferred are 3 to 25 percent by weightof ahydroxyl groups-containing monomer, and

a3) 0 to 80 percent by weight of further monomers with a polymerizableolefinic unsaturated double bond,

wherein the sum of all monomers is 100 percent by weight, in an organicsolvent at 70° to 130° C., preferably at 80° to 120° C., using at least0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and using polymerization initiators, wherein thepolymerization for the production of the acrylate copolymer is socarried out that a solution of the polymer with a solid content of 40 to65 percent by weight results, and from

a12) monoisocyanates with a tertiary amino group in the molecule,

wherein the proportions of the individual components are so selectedthat between the carboxyl groups of component A) and the epoxide groupsof component B) a molar ratio of 3:1 and 1:3 obtains and that betweenthe epoxide resin component and the aminoplastic resin component a ratioof weight of 65:35 percent by weight to 98:2 percent by weight obtains.

As component a12) addition products of diisocyanates with amino alcoholsare possible such as, for example, dimethyl- and diethylamino ethanol.Thetertiary amino group can, for example, also be introduced through2-hydroxyethyl pyridine. Particularly preferred is an addition productof isophorondiiscyanate with amino alcohols as component a12).

According to a preferred embodiment of the invention component A) can beobtained by the copolymerization of

a1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds,

a2) 0 to 40 percent by weight, preferred are 5 to 30 percent by weight,of a carboxyl groups-containing monomer,

a5) 8 to 50 percent by weight, preferred are 10 to 40 percent by weight,ofa hydroxyl groups-containing monomers,

a3) 0 to 80 percent by weight of further polymerizable monomers with anolefinic unsaturated double bond,

wherein the sum of all monomers is 100 percent by weight, in an organicsolvent at 70° to 130° C., preferably at 80° to 120° C., using at least0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and using polymerization initiators, wherein thepolymerization for the production of the acrylate copolymer is socarried out that a solution of the polymer with a solid content of 40 to65 percent by weight results, and from

a12) monoisocyanates with a tertiary amino group in the molecule andfrom

a6) cyclic carboxylic anhydrides,

wherein the proportions of the individual components are so selectedthat between the carboxyl groups of component A) and the epoxide groupsof component B) a molar ratio of 3:1 to 1:3 obtains and that between theepoxide resin component and the aminoplastic resin component a weightratio of 65:35 percent by weight to 98:2 percent by weight obtains.

In the event that the component B) is based on a soluble branchedacrylate copolymer, it is obtained by copolymerisation of

b1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of a monomer with at least two polymerizable olefinic unsaturated doublebonds,

b2) 5 to 50 percent by weight, preferred are 10 to 40 percent by weight,ofmonomers with an epoxide group, and

b3) at least 10 percent by weight of further monomers with apolymerizable olefinic unsaturated double bond,

wherein the sum of b1) to b3) is 100 percent by weight, in an organicsolvent at 70° to 130° C., preferably at 80° to 120° C., using at least0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and using polymerization initiators where the polymerizationfor the production of the acrylate copolymer is so carried out that asolution of the polymer with a solid content of 40 to 65 percent byweight results, wherein the proportions of the individual components areso selected that between the carboxyl groups of component A) and theepoxide groups of component B) a molar ratio of 3:1 to 1:3 obtains andthat between the epoxide resin component and the aminoplastic resincomponent a ratio of weight of 65:35 percent by weight to 98:2 percentby weight obtains.

As component b2) glycidyl esters of unsaturated carboxylic acids orglycidyl ethers of unsaturated compouns are preferably used. As examplesmay be named: glycidyl acrylate, glycidyl methacrylate, glycidyl estersofmaleic and fumaric acid, glycidyl vinyl phthalate, glycidyl allylphthalate, and glycidyl allyl malonate.

Component B) is likewise obtained by copolymerization of

b1) 5 to 30 percent by weight, preferred are 5 to 25 percent by weight,of monomers with at least two polymerizable olefinic unsaturated doublebonds,

b4) 5 to 50 percent by weight, preferred are 10 to 40 percent by weight,ofmonomers with at least one polymerizable double bond and a functionalgroupF,

b3) further polymerizable monomers,

wherein the sum of b1) to b3) is 100 percent by weight, in an organicsolvent at 70° to 1300° C., preferably at 80° to 120° C., using at least0.5 percent by weight, preferably at least 2.5 percent by weight,relative to the total weight of the monomers, of apolymerizationregulator and using polymerization initiators, wherein thepolymerization for the production of acrylate copolymer is so carriedout that a solution of the polymer having a solid content of 40 to 65percent by weight results, and from

b5) an organic compound with at least one epoxide group and one groupreactive with the functional group F of the monomers from b4),

wherein the proportions of the individual components are so selectedthat between the carboxyl groups of component A) and the epoxide groupsof component B) a molar ratio of 3:1 to 1:3 obtains and that between theepoxide resin component and the aminoplastic resin component a weightratio of 65:35 percent by weight to 98:2 percent by weight obtains.

As component b4) and b5) monomers are possible with an isocyanate group(b4), as well as isocyanatoethyl methacrylate and isocyanatobutylmethacrylate as well as epoxypropanol (b5) or also carboxylic acidmonomers (b4) and di- or polyepoxide compounds (b5).

When b4) is an isocyanate ester, F is an isocyanate, and when b4) is acarboxylic acid monomer, F is a carboxylic acid group.

When using carboxyl groups-containing monomers as component b4,preferably β-carboxyethyl acrylate is used proportionally. The carboxylgroups-containing monomer is advantageously proportionally a monomerwith phosphoric acid groups.

The pre-crosslinked soluble acrylate copolymers A) or B) are produced inthat the monomers are copolymerized in an organic solvent at 70° to130°C., preferably at 80° to 120° C., using at least 0.5 percent by weight,preferably at least 2.5 percent by weight, relativeto the total weightof the monomers, of a polymerization regulator and using polymerizationinitiators to form a pre-crosslinked branched but notgalled product. Ifnecessary, following the radical copolymerization can take place theconversion with the cyclic carboxylic anhydrides, the conversion withthe compounds which contain at last one hydrogen able to react with acidanhydride groups as well as also at least one tertiary amino group aswell as possibly with monofunctional compounds with active hydrogen oralso the conversion with the secondary amines or the di- or polyamineswith at least one tertiary amino group and one primary or secondaryamino group and/or with carboxylic acids which contain one tertiarynitrogen as well as with the cyclic carboxylic anhydrides or possiblywith the monoisocyanates containing one tertiary nitrogen group in themolecule, or also following the copolymerization with themonoisocyanates having a tertiary nitrogen group in the molecule and theconversion with cyclic carboxylic anhydrides or the conversion of acompound with at least one epoxide group and a group able to react withthe functional group F of monomer b4).

It must be observed in the production of the acrylate copolymer that apre-crosslinked but not gelled copolymer is obtained. Throughappropriate polymerization conditions, surprisingly, a clear,transparent, non-galled solution of a branched copolymer can beproduced. Through the use of monomers with at least two ethylenicunsaturated groups a pre-crosslinkingof the copolymer molecules isbrought about which, due to the special reaction conditions according tothe invention, nevertherless do not lead to gelled products.

The polymerization is so carried out that a solution of the polymer witha solid content of 40 to 65 percent by weight results. The solid contentis a function of the fraction of monopolymerized, multiply ethylenicunsaturated monomers. If this fraction is low, then polymerization cantake place at greater solid contents. It is furthermore necessary to usesuitable initiators and, depending on the fraction of difunctionalmonomers, at least 0.5 percent by weight, preferably however, at least2.5percent by weight, of a polymerization regulator. The choice ofinitiator depends on the fraction of difunctional monomers used. Withlow fraction the initiators customary for such temperatures, such asperoxy esters, canbe used. With greater fraction of difunctional monomerinitiators such as for example azo compounds, are preferably used. Afterthe polymerization the polymer solution is concentrated to the desiredcolid content by separation by distillation of the solvent, preferableto solid contents of60 percent by weight. The so obtained clearcopolymer solutions have, adjusted to a solid content of 50 percent byweight, a viscosity of 0.4 to10 dPas.

The polymerization is carried out in the presence of an organic solvent.Examples are ethanol, isopropanol, n-propanol, n-butanol, isobutanol,t-butanol, methyl, ethyl, propyl, and butyl esters of acetic acid,acetone, methylethyl ketone, xylene, toluene.

Suitable as polymerization regulators are preferably mercaptogroups-containing compounds, wherein particularly preferredmercaptoethanol is used. Other possible regulators are, for example,t-dodecylmercaptan, phenylmercaptan, octyldecylmercaptan,butylmarcaptan, and thiocarboxylic acids such as perhaps thiolacticacid.

In the production of the acrylate copolymer according to certain aspectsofthe invention no hydroxy mercaptans or mercaptans having primary --SHgroups are to be used as polymerization regulators. In the choice of thepolymerization regulator in the production of the acrylates according toother aspects of the invention, care should be taken that nothiocarboxylic acids are used.

As component C) (aminoplastic resin) melamine formaldehyde resins, ureaformaldehyde resins, and benzoguanamine resins are possible. These canbe fully to partially methylolated, but can also still contain free --NHgroups. As component C) partially and fully etherified resins can beused.Use of mixed etherified products is often of advantage. Asetherification alcohol methanol, ethanol, propanol, iso-butanol,n-butanol, and ethylhexanol are possible.

The present invention also relates to a method for the production of thecurable previously described compounds, characterized in that thepolymer is mixed with at least two epoxide groups B) and theaminoplastic resin C)in an organic solvent and that this mixture ismixed with the COOH polymer A) before being processed.

The invention also relates to coating materials which are characterizedin that they contain the previously described curable compounds, ifnecessarycatalysts, organic solvents, if necessary, pigments andcustomary auxiliaryagent and additives.

If the catalyst for the epoxy-carboxy cross-linkage is incorporated intothe polymer, then the quantity depends on the desired bakingtemperature. At increased temperatures less tertiary amine isincorporated, at low baking temperature more. of the tertiary amine isincorporated.

When using the coatings for transparent lacquer aliphatic amines shouldprimarily be incorporated, since aromatic amines often lead todiscolorations. It is understood, that additionally external catalystscanalso be used. Suitable catalysts are metal salts, for examplechromium compounds, aluminum- and titanium compounds.

The baking temperatures of the described curable compounds are ingeneral 80° to 180° C. Through the fraction of incorporated catalyststhe coating materials can advantageously be adjusted to the desiredbaking temperature.

The described curable compositions yield coatings with excellentpropertieswith respect to resistance to long-term stress by solvents,chemicals, water or water vapor, and with respect to hardness andelasticity.

In addition, a relatively high solid content of the curable coatingmaterials is achieved at relatively low viscosity.

The coating materials based on the described curable composition can beapplied as filler, covering lacquer and as base and/or transparentlacquerof a metallic multilayer lacquer.

The invention is explained below in greater detail in conjunction withembodiment examples:

The viscosity values were determined on a Plate-Cone viscosimeter at 23°C., the solid values were determined in a forced-air oven, if not statedotherwise, at 1 hour at 130° C. The acid numbers are given in mg KOH/gresin and refer to the solid resin. The epoxide equivalent weights referlikewise to solid resin.

PRODUCTION OF COPOLYMER SOLUTIONS ACCORDING TO THE INVENTION Productionof a Branched COOH Acrylate, A1

Into a 4 liter high-grade steel boiler are placed

376.8 parts xylene

376.8 parts butanol

188.4 parts methylisobutyl ketone

Weighed and mixed in the monomer tank are

100 parts methyl methacrylate

100 parts n-butyl acrylate

170 parts tert-butyl acrylate

100 parts ethylhexyl acrylate

100 parts styrene

200 parts hexanediol dimethacrylate

200 parts acrylic acid

30 parts dimethylaminoethyl methacrylate

50 parts mercaptoethanol

Weighed and mixed in the initiator tank are:

36.0 parts 2,2'-azobis(2-methylbutanonitrile)

57.6 parts xylene

57.6 parts butanol

28.8 parts methylisobutyl ketone

The receiving vessel is heated to 110° C. and the monomer tank isapportioned uniformly over a period of 3 hours, the initiator tank isapportioned uniformly over 3.5 hours. Both feeds are startedsimultaneously. During the polymerization the temperature is maintainedat110° C., following the end of the feed, after-polymerization takesplace for another 2.5 hours. The thus obtained clear solution of thebranched acrylate has a viscosity of 2.2 dPas (230° C.), a solid contentof 49.6%, and an acid number of 132.6.

Production of a Glycidyl Groups-containing Acrylate B1

Into a 4 liter high-grade steel boiler are placled and heated to 110°C.:

282.9 parts xylene

565.8 parts 1-methoxypropyl-2-acetate

Feed 1:

270 parts glycidyl methacrylate

Feed 2:

135 parts methyl methacrylate

90 parts styrene

180 parts n-butyl acrylate

135 parts hexanediol diacrylate

45 parts ethylhexyl acrylate

45 parts hyrodypropyl methacrylate

40.5 parts mercaptoethanol

Feed 3:

40.8 parts xylene

81.6 parts 1-methoxypropyl-2-acetate

30.6 parts 2,2'-azobis(2-methylbutanonitrile)

Feeds 1, 2, and 3 are started simultaneously; feed 1 is apportioneduniformly in portions over 2.5 hours, feed 2 over three hours, feed 3over3.5 hours. During the polymerization the temperature is kept at110°C., subsequently after polymerization takes place for an additional3 hoursat 110° C. Subsequently 330 parts of the solvent mixture aredistilled off. The so obtained clear solution of the glycidylgroups-containing acrylate resin has a solid content of 58.8, aviscosity of 8.0 dPas, and an epoxide equivalent weight of 561.

Production of the Glycidyl Groups-containing Acrylate B2

Into a 4 liter high-grade steel boiler are placed and heated to 110°C:

282.9 parts xylene

565.8 parts 1-methoxypropyl-2-acetate

Weighed and mixed in the individual feed tanks are:

Feed 1: 270 parts glycidyl methacrylate

Feed 2: 45 parts hydroxypropyl methacrylate

Feed 3:

135 parts methyl methacrylate

90 parts styrene

180 parts n-butyl acrylate

135 parts hexanediol diacrylate

45 parts ethylhexyl acrylate

40.5 parts mercaptoethanol

Feed 4:

40.8 parts xylene

81.6 parts 1-methoxypropyl-2-acetate

30.6 parts 2,2'-azobis(2-methylbutanonitrile)

Feeds 1, 3, and 4 are started simultaneously. Feed 1 is apportioned over2.5 hours, feed 3 over 3 hours, feed 4 over 3.5 hours. Feed 2 is startedafter the end of feed 1 and added over 0.5 hours. During thepolymerization the temperature is maintained at 110° C.,after-polymerization takes place subsequently for another 3 hours. 326parts of the solvent mixture are distilled off. The thus obtained clearacrylate resin solution has a solid content of 59.2%, a viscosity of 9.5dPas, and an epoxide equivalent weight of 553.

Transparent lacquer 1: 91.7 parts of the resin solution B2 according totheinvention are mixed with 13.8 parts of a methanol/butanol mixedetherified melamine resin (Cymel 1130) and subsequently added to 85.14parts of the acrylate resin solution A1.

Transparent lacquer 2: 94.12 parts of the resin solution B1 are mixedwith 14 parts cf a butanol part-etherified melamine resin (Cymel 1158),subsequently 85.14 parts of the COOH acrylate solution A1 are added.

The lacquers are diluted with a small amount of pentanol and squeegeedontosheets of glass at a wet film thickness of 100 μm. The films arebaked for 30 minutes at 1200° C.

Transparent lacquer 1: 2 hours after oven: pendulum hardness 120.4seconds,5 minutes high-grade gasoline

Transparent lacquer 2: 2 hours after oven: Pendulum hardness 187.6seconds,5 minutes high-grade gasoline f.i.O.

I claim:
 1. A curable composition comprising:A) a polymer having atleast tow --COOH groups, B) a polymer having at least two epoxidegroups, and C) an aminoplastic resin,characterized in that as componentA) a soluble branched acrylate copolymer is obtained by copolymerizationof: a1) 5 to 30 percent by weight of a monomer with at least twopolymerizable olefinic unsaturated double bonds wherein di- andpolyesters of di- and polyols with acrylic acid are excluded, a2) 3 to50 percent by weight of a carboxylic groups-containing monomer, a4) 0.1to 20 percent by weight of a tertiary amine with a polymerizableolefinic unsaturated double bond, a5) 0 to 40 percent by weight of ahydroxyl groups-containing monomer, and a3) 0 to 80 percent by weight ofa further monomer with a polymerizable olefinic unsaturated double bond,wherein the sum of components a1), a2), a3), a4) and a5) is 100 percentby weight and at least one of the components a1), a2), a3), a4) and a5)is an acrylate monomer, in an organic solvent at 70° to 130° C., usingat least 0.5 percent by weight relative to the total weight of themonomers, of a polymerization regulator and using a polymerizationinitiator, wherein the polymerization of the acrylate copolymer iscarried out so that a solution of the polymer with a solid content of 40to 65 percent by weight results, wherein the proportions of theindividual components to each other are so selected that between thecarboxyl groups of component A) and the epoxide groups of component B) amolar ratio of 3:1 to 1:3 is obtained and that between the epoxide resincomponent and the aminoplastic resin component a wight ratio of 65:35percent by weight to 98:2 percent by weight is obtained.
 2. A curablecomposition comprising:A) a polymer having at least two --COOH groups,B) a polymer having at least two epoxide groups, and C) an aminoplasticresin,characterized in that component B) is a soluble branched acrylatecopolymer obtained by copolymerization of: b1) 5 to 30 percent by weightof a monomer having at least two polymerizable olefinic unsaturateddouble bonds, b2) 5 to 50 percent by weight of a monomer having anepoxide group, and b3) at least 10 percent by weight of an additionalmonomer having a polymerizable, olefinic unsaturated double bond,wherein at least one of the components b1), b2) and b3) is an acrylatemonomer and the sum of components b1), b2) and b3) is 100 percent byweight, in an organic solvent at 70° to 130° C., using at least 0.5percent by weight, relative to the total weight of the monomers, of apolymerization regulator and using a polymerization initiator, whereinthe polymerization is carried out so that a solution of the polymerresults having a solid content of 40 to 65 percent by weight, whereinthe proportions of the individual components are selected so thatbetween the carboxylic groups of component A) and the epoxide groups ofcomponent B) a molar ratio of 3:1 to 1:3 is obtained and that betweenthe epoxide resin component and the aminoplastic resin component aweight ratio of 65:35 percent by weight to 98:2 percent by weight isobtained.
 3. A curable composition comprising:A) a polymer having atleast two --COOH groups, B) a polymer having at least two epoxidegroups, and C) an aminoplastic resin,characterized in that component B)is a soluble branched acrylate copolymer obtained by copolymerizationof: b1) 5 to 30 percent by weight of a monomer having at least twopolymerizable olefinic unsaturated double bonds, 4) 5 to 50 percent byweight of a monomer having at least one polymerizable double bond andone functional group F, wherein F is a carboxylic acid or an isocyanategroup, and b3) a further polymerizable monomer, wherein the sum ofcomponents b1), b4) and b3) is 100 percent by weight, in an organicsolvent at 70° to 130° C., using at least 0.5 percent by weight,relative to the total weight of the monomers, of a polymerizationregulator and using a polymerization initiator, wherein thepolymerization of the acrylate copolymer is carried out so that asolution of the polymer results having a solid content of 40 to 65percent by weight which is then reacted with b5) an organic compoundhaving at least one epoxide group and one hydroxyl or epoxy groupreactive with the functional group F of the monomers from b4), andwherein the proportions of the individual components are selected sothat between the carboxylic groups of component A) and the epoxidegroups of component B) a molar ratio of 3:1 to 1:3 is obtained and thatbetween the epoxide resin component and the aminoplastic resin componenta weight ratio of 65:35 percent by weight of 98:2 percent by weight isobtained.
 4. A curable composition as stated in claim 1, characterizedin that the component a1) corresponds to the formula ##STR4## in whichX═O, NR' or S with R'=H, alkyl, aryl, andn=2 to 8 or a divinyl compound.5. A curable composition as stated in claim 1, characterized in that thecarboxyl groups-containing monomer (a2) comprises B-carboxyethylacrylate.
 6. A curable composition as stated in claim 1, characterizedin that the carboxyl groups-containing monomer (a2) comprises a monomerwith phosphoric acid groups.
 7. A curable composition as described inone of claim 1, 2 and 3 characterized in that the monomer (a3) or (b3)is selected from the group consisting of styrene, vinyl toluene, alkylesters of acrylic acid and methacrylic acid, alkoxyalkyl acrylate andaryloxyalkyl acrylate and the corresponding methacrylates, esters ofmaleic, fumaric, crotonic, and dimethyl acrylic acid.
 8. A coatingcomposition as described in any one of claims 1, 2 and 3 whereinpolymerization of the soluble branched acrylate copolymer (A) or (B) isconducted at a temperature in the range of 80° C. to 120° C.
 9. Acoating composition in accordance with any one of claim 1, 2 and 3wherein the branched acrylate copolymer is in the form of apre-crosslinked polymer solution.
 10. A process for the preparation of acurable composition as claimed in any one of claims 1, 2, or 3,comprising the steps of:(1) mixing component B) and component C) in theorganic solvent, then (2) adding component A) into the organic solventwherein the polymerization of component A) is carried out.